The inclusion of light absorbing compounds in silver halide emulsion layers or other hydrophilic colloid layers to absorb light of a specified wavelength has generally been a characteristic of silver halide photographic materials in the past for the purpose of adjusting speed, increasing the level of safety to safe-lighting, adjusting the color temperature of light, preventing halation, or for adjusting the speed balance in multi-layer color photographic materials.
For example, silver halide photographic materials consist of hydrophilic colloid layers such as light-sensitive silver halide emulsion layers which are formed on a support, but when imagewise exposures are made to record images in the light-sensitive silver halide emulsion layers it is necessary to control the spectral composition of the light which is directed onto the silver halide emulsion layers in order to increase the photographic speed. In such a case, use is made of a method in which a dye which absorbs light of the wavelength region which is not required in the silver halide emulsion layer is included in a hydrophilic colloid layer which is located on the side farther away from the support than the aforementioned light-sensitive silver halide emulsion layer as a filter layer so that only light in the wavelength region which is required is transmitted to the silver halide emulsion layer.
Furthermore, an anti-halation layer is intended to improve image sharpness and such a layer is positioned between the light-sensitive emulsion layer and the support, or on the back of the support, where it absorbs harmful reflections from the interface between the emulsion layer and the support or from the back of the support, and thereby increases image sharpness.
Further, dyes which absorb light in the wavelength region to which the silver halide is sensitive can be used in the silver halide emulsion layers for anti-irradiation purposes in order to increase image sharpness.
Moreover, dyes which absorb UV light and visible light can be added to a light-sensitive layer or to a layer which is positioned between the light source and a light-sensitive layer in order to raise the level of safety with respect to safe-lights of the silver halide photographic materials, and more precisely the light-sensitive materials for bright room, which are used in photomechanical processes.
Furthermore, the dyes may be added to hydrophilic colloid layers which are positioned between the light-sensitive silver halide emulsion layer and the support for anti-halation purposes.
The dyes which are used for such purposes must satisfy a number of conditions. Thus, they must be decolorized during the photographic development process, readily dissolve out of the silver halide photographic material, and there should be essentially no residual color staining by the dye after processing. Moreover, they should not have any adverse effects on the photographic emulsion, such as fogging or desensitization, etc.; they should not diffuse from the colored layer into other layers; they should have appropriate spectral absorption characteristics for the intended purpose; and they should have excellent stability with respect to the passage of time in solution or in the silver halide photographic material with no degeneration.
Much work has been done in connection with the discovery of dyes which satisfy these conditions. For example, there are the pyrazolone oxonol dyes disclosed in British Pat. 506,385, the barbituric acid oxonol dyes disclosed in U.S. Pat. 3,247,127, the azo dyes disclosed in U.S. Pat. 2,390,707, the styryl dyes disclosed in U.S. Pat. 2,255,077, the hemioxonol dyes disclosed in British Pat. 584,609, the merocyanine dyes disclosed in U.S. Pat. 2,493,747, the cyanine dyes disclosed in U.S. Pat. 2,843,486, the methylene type benzylidene dyes disclosed in U.S. Pat. 4,420,555, etc.
In cases where layers which contain the above mentioned dyes function as filter layers or anti-halation layers, the layer must be colored selectively and there must be effectively no coloration of the other layers. This is because if other layers are colored, not only does this have a spectrally harmful effect on the other layers but it also reduces the effectiveness of the layer as a filter layer or anti-halation layer. Furthermore, if a dye which has been added to a certain layer for preventing irradiation diffuses out of the layer and colors other layers, this also gives rise to problems of the same type as mentioned above.
Methods in which a so-called acidic dye which has sulfo groups or carboxyl groups is localized in a specified layer using a mordant were known in the past as a means of overcoming this problem.
The ethylenic unsaturated compound polymers which have dialkylaminoalkyl ester residual groups disclosed in British Pat. 685,475, the reaction products of poly(vinyl alkyl ketones) and aminoguanidine disclosed in British Pat. 850,281, and the vinylpyridine polymers and vinylpyridinium cation polymers disclosed in the specifications of U.S. Pats. 2,548,564, 2,484,430 3,148,061 and 3,756,814 etc. are known as mordants of this type, and cation based mordants in which secondary or tatiary amino groups, nitrogen-containing heterocyclic groups and quaternary cations thereof are contained in a polymer can be used in such a way as to fix effectively the acidic dyes mentioned earlier.
However, these cation based mordants undergo an electrostatic interaction with gelatin which is often used as the hydrophilic colloid and with the surfactants which have alcoholate groups, carboxylate groups, sulfonate groups or sulfate groups which are normally employed as coating aids and there have been cases in which this has had an adverse effect on coating properties.
There have also been cases where these compounds have caused a poor desilvering and reduced speed in adjacent emulsion layers in color light-sensitive materials.
Furthermore, the acidic dyes mentioned earlier have often been observed to diffuse into other layers with mordants of this type and the use of large amounts of mordant has been considered as a way of stopping this diffusion. However not only is it impossible to stop diffusion from occurring completely with this method but it also increases the thickness of the layer in which the mordant is present and this is disadvantageous in that it inevitably results in reduced sharpness.
Moreover, with the sensitive materials used for photomechanical processes of printing, the operation in which a reducing bath is used known as reduction, is normally carried out in order to adjust density, gradation, etc. However water-soluble iron complexes are present in such reducing baths as reducers, and when a cation based mordant of the type mentioned earlier is used, it bonds electrostatically with the iron complexes and this is disadvantageous in that it results in yellow staining by the iron complex.